It really depends on the circumstances. I am a firm believer in Murphy. Stuff happens. So I try to be reasonable, will reach out a time or two if no response, especially if it is somebody I would consider a regular. If it is a first time meet, then I will assume the individual is a flake (no matter how much I looked forward to meeting), thank my lucky stars for figuring it out sooner, rather than later, and move on. In the circumstances you outlined, I assume it is a first time meet, so I would declare it a loss and move on. Find somebody else. I try to be respectful of other people's time - and expect the same in return. Don't let it ruin your trip! Post script - please consider submitting a review, you may save a forum member some drama!